High attenuation shielded lead structure



Feb. 16, 1954 s. P. BIRD HIGH ATTENUATION SHIELDED LEAD STRUCTURE Filed Sept. 23, 1952 St'dnf zzBir Patented Feb. 16, 1954 HIGH ATTENUATION SHIELDED LEAD STRUCTURE Stanley P. Bird, Verona, N. J., assignor to Breeze Corporations, Inc., Newark, N. J a corporation of New Jersey Application September 23, 1952, Serial No. 311,077

6 Claims.

This invention relates to shielded ignition leads, such as are used for radio shielding the ignition systems of turbo-jet combustion engines and the like.

Where the ignition systems of internal combustion engines are radio shielded, and particularly where they are applied to high energy, low voltage ignition systems, various problems arise which reduce the efiiciency and life of said shielding elements.

Accordingly, it is an object of the present invention to provide a high attenuation, shielded lead assembly which will prevent leakage current from being conducted to the outside of the system, as well as providing an increased number of reflection surfaces in said structure.

A further object of this invention is to provide a shielded lead assembly which may employ different materials therein, without fear of galvanic action.

Another object of the present invention is to provide a shield which will cover a broad frequency range because of its increased resistance to direct penetration, as well as the increased number of reflective surfaces.

A feature of the present invention is its light, watertight construction.

Another feature of the present invention is its use of alternate layers of electrical conductive and dielectric material.

A further feature of the present invention is its use of dissimilar ferrules which co-operate with the shielding layers to provide long path attenuation wave guides.

The invention consists of the construction, combination and arrangement of parts, as herein illustrated, described and claimed.

In the accompanying drawings, forming a part hereof, is illustrated one form of embodiment of the invention, in which drawings similar reference characters designate corresponding parts, and in which:

Figure 1 is a view in side elevation of a complete embodiment of the invention, partially cut away to show its construction.

Figure 2 is a vertical section, taken on line 2-2 in Figure 1.

Referring to the drawings, l0 indicates a spirally wound and soldered conduit, such as is well known in the radio shielding art, and which is adapted to receive therein a dielectric covered ignition wire (not shown). The conduit I0 is covered with a layer of dielectric material H, which may be in the nature of a glass braid impregnated with a suitable binder such as silicone resin adapted to keep it in place during the cutting and trimming operations. The glass braid may be applied as a sleeve, as a helically wrapped tape, or as a woven braid similar to the metallic is applied over the dielectric covering H, and alternate successive layers may thereafter be applied in any suitable and desired number. Four of such layers of dielectric and conductive material are shown for the purpose of illustration, but it is within the contemplation of the present invention to employ two or more layers, depending upon the overall degree of attenuation desired.

It is also within the purview of the present invention to employ layers of iron braid, and also copper braid, in the same structure, to achieve the desired results. Thus, for example, using copper as the last layer, will give the structure the increased reflection loss from copper to air, while employing the gains in attenuation caused by the relative permeability of iron. A sleeve 13 of dielectric material is provided around the last layer of metallic braid 12.

After the conduit 10 is covered in the manner previously described, the ends of the covers are trimmed, so as to leave exposed at one end thereof, conductive layers, indicated as A and C. At the opposite ends the conductive layers B and D may be exposed, while the other layers of conductive material remain covered by the overlying dielectric material, as shown.

The ferrules l4 and i5, which are adapted to go over each end of the shielded lead, are dis similar in structure, in that the ferrule 34 is provided with internal steps 1%, which are so constructed as to make contact with the conduit l0, and the exposed conductive layers A and C. The steps ll of the ferrule l5 are of such size as to make contact with the conduit it, and members B and D. The ferrules i4 and I5 are suitably secured to the conductive layers, as by silversoldering, in the well known manner.

No contact between successive conductive braids is allowed to exist, except as arranged by the assembly of the ferrules l4 and IS on thebraided conduit, as shown.

While the foregoing constitutes a suitable method of forming the structure shown, it will be apparent that many other arrangements and methods may be used to form this contact relationship, in order to have the braids joined in their proper order. It will thus be seen that there has been formed a series of attenuation wave guides, with no possibility of ground loops to prevent leakage current from being conducted to the outside of the lead, and which will increase by a factor, depending upon the number of metal layers, the reflection surfaces presented to the electric and magnetic waves that penetrate the conduit l0.

Further, the separate layers, although constructed of different materials, will not succumb to galvanic action which would permit corrosion braid l2, as shown. The layer of metal braid [2 so within the lead.

The high attenuation attainable by this construction,'will make this type of shield applicable to the new high energy, low voltage ignition systems currently in favor.

Ground loops which develop between old and tarnished braids, and in thoseloosened by mechanical vibrations, will be prevented from developing within a structure such as has herein.

been described.

The soldered construction at each end of the lead, whereby the ferrules l4 and I are secured to the conduit, provides a watertight structure as well as a direct return path for the high energy ignition currents. The sleeve I3 which isswaged tightly underneath both ferrules l4 and i5 also serves to restrict moisture absorption from the outside.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent of the United States, is:

l. A high attenuaticnshield-ing s'tructure for ignition leads comprising, a lead receiving-com duit, alternate layers of conductive and nonconductive material disposed about the conduit,

a first ferrule on one end of the structure, said.

first ferrule having a plurality of steps therein, said steps being formed so as to overlie and be in electrical contact with the conduit and alternate conductive layers within the structure, a second ferrule on the end of the structure opposite thefirst ferrule, said-second ferrule having a plurality of steps therein, said steps having a diameter which cause them to overlie and come into electrical contact with the conduit and those conductive layers within the structure not soontacted by the first ferrule, and a protective dielectric covering surrounding the assembly :between the ferrules.

2. A high attenuation shielding structure for ignition leads comprising, a lead receiving, conduit, alternate layers of conductive and; nonconductive material disposed about the-tconduit, said conductive layers being formedof metallic braid, a first ferrule on one endof thestructure, said first ferrule having a plurality of steps therein, said steps being formed so as to overlie and be in electrical contact with the conduitand with alternate conductive layers within the structure, asecond ferrule on the end of thestructure opposite the first ferrule, said. second ferrule having a plurality of steps therein, said steps having a diameter which will cause them to overlie and come into, electrical contact with the con duit and with thoseconductive layers within the structure not contacted by the firstzferrule;

and a protective dielectric covering surrounding the assembly between the ferrules.

3.. A high attenuation shielding structure' for ignition leads comprising, a lead receiving-conduit, alternate layers of conductive and nonconductive material disposed about the conduit, said conductive layers being formed iofmetallic braid, and the outermost conductive layer con sisting of copper wire braid, a first ferruleyon one end of the structure, said first ferrule :having a plurality of steps therein, said stepsnbeing formed so as to overlie. and .be in electrical contact with the conduit and with alternate vconductive layers within the structure, a second ferrule on the end of the structure opposite .the first ferrule, said second ferrule having-a plurality of steps therein, said steps, having, a diameter which will cause them tozoverliewand come into electrical contact with the conduit and with those conductive layers within the structure not contacted by the first ferrule, and a protective dielectric covering surrounding the assembly between the ferrules.

4. A high attenuation shielding structure for ignition leads comprising, a lead receiving conduit, alternate layers of conductive and nonconductive material disposed about the conduit, at least one of said conductive layers being formed of metallic braid of different composition fromthe others, a first ferrule on one end of the structure, said first ferrule having a plurality: of steps therein, said steps being formed so as to overlie and be in electrical contact with the conduit with alternate conductive layers within the structure, a second ferrule on the end ofthe structure opposite the first ferrule, said second ferrule having a plurality of steps there in, said steps having a diameter which will cause them to overlie and come into electrical contact with the conduit and with those conductive layers within the structure not contacted by the first ferrule, and a protective dielectric covering surrounding the assembly between the ferrules :5. A high attenuation shielding structure for ignition leads comprising, a lead receiving, -.elec trically conductive conduit, alternate layers of conductive and non-conductive material disposed about the conduit, a first ferrule on one end of the structure, said first ferrule having a pin ralitylof steps therein, said steps being formed so as to overlie andbe in electrical :contact with alternate conductive layers including the conduit within the structure, asecond ferrule on theend of the structure opposite the first ferrule, said second ferrule having a plurality ofusteps therein, said steps havinga diameter which will cause them to overlie andcome into electrical contact with the conduit and with those condnctiveilayers within the structure not contacted by the first ferrule, and a protective dielectric covering surrounding the assembly between the ferrules.

6. A high attenuation shielding structure for ignition leads-comprising, a lead receiving, electrically conductive conduit, alternate layers ofconductive and. non-conductive material disposed about the conduit, at least-one of said conductive layers being formed of metallic braid. of different composition from the others, and the outermost conductive layerconsistin-g of copper wire braid, a first ferrule onone end of the structure, said first ferrule having a plurality of steps therein, said steps being formed so as to overlie andwbe in electrical contact wtih alternate conductive layers including the conduit within the structure, arsecondf'erru'le on. the end of the structureopposite the first ferrule, said second ferrule having a plurality of steps therein, said steps having a diameter which will cause them to overlie/and come into electrical contact with the conduit and with those conductive layers within the structure not contacted by the first ferrule, anda-protective dielectric covering surrounding the assembly between the ferrules.

Tyzzer May '15, 1 945 

